The preparation of textured polyester multifilament yarns has been carried out commercially on a worldwide scale for many years. The simultaneous draw-texturing by a false-twist texturing process of partially oriented feed yarns of low crystallinity prepared by spin-orienting, i.e., withdrawing the melt-spun polyester filaments at high withdrawal speeds of, e.g., 3,000 ypm, was disclosed by Petrille in U.S. Pat. No. 3,771,307, and the feed yarns were disclosed by Piazza and Reese in U.S. Pat. No. 3,772,872. Use of these spin-oriented feed yarns has made possible significant increases in texturing speeds. In about 1970, commercially-available texturing machines (false-twist texturing) were capable of maximum speeds only of the order of about 200 mpm (meters per minute). For several years now, owing to improvements in machinery design, draw-texturing machines have been commercially available with a capability of operating at very high speeds of, e.g., 1,000 mpm or more. Despite the availability of such machines, capable of machine operation at such desirable very high speeds, commercially-available draw-texturing polyester feed yarns (DTFY) have not been textured commercially at the very high speeds of which the machines are capable. This is mainly because of the excessive number of broken filaments produced at these very high speeds. Any broken filaments are undesirable, since they may cause difficulties, and even yarn breaks, during subsequent processing, and also fabric defects. The number of broken filaments that may be tolerated in practice will depend upon the intended use for the textured yarn and eventual fabric. In practice, in the trade, the ends of the bobbin are examined for broken filaments, and the number of protruding broken filaments is counted so as to give a measure of the probable number of broken filaments in the yarn of that package. The total number of these broken filaments counted is then divided by the number of pounds in the package and expressed as BFC. For certain end uses, the maximum that can be tolerated is between 0.5 and 0.6 BFC, i.e., between 5 and 6 broken filaments for every 10 lbs. of polyester yarn, it being understood that one break will probably count as two broken filaments. Thus, for any texturer having a texturing machine capable of operation at 1,000 mpm or more, if the polyester draw-texturing feed yarns commercially available cannot be processed on this machine at more than about 850 mpm without significantly exceeding the desired maximum (e.g.,about 0.5 BFC), he will be forced in practice to operate his machines at this speed of 850 mpm instead of increasing the speed to the maximum capability of the machine. Despite the obvious commercial incentive to provide polyester draw-texturing feed yarns capable of being draw-textured at speeds of more than 1,000 mpm without excessive BFC, however, hitherto, this problem of providing a commercially-satisfactory feed yarn has not yet been solved.
I have found it possible to increase texturing speeds without causing excessive broken filaments by increasing the withdrawal speed used to obtain the desired spin-orientation in the feed yarn. Such feed yarns, prepared at relatively high withdrawal speeds of 4,000 mpm, have not been textured commercially on a large scale because of accompanying disadvantages, mainly that the resulting textured yarns have not been as bulky as yarns that are already available commercially. Bulk is generally measured as CCA, a value of at least about 4 being considered desirable, or as TYT, a value of over 20 being considered desirable, generally, at this time.
The problem that has faced the industry, therefore, has been to provide a polyester multifilament draw-texturing feed yarn (DTFY) that is capable of being draw-textured on existing commercial machines at a speed of at least 1,000 mpm and yet of providing a package of textured yarn with, by way of example, not more than about 0.5 BFC and over 20 TYT, it being understood that such figures depend very much on economic and other commercial considerations and on what competitors are prepared to offer at any time. Generally, with the passage of time, the demands of any industry tend to increase.